In general, fuel injection nozzle valves operate in response to high pressure fuel creating forces acting on differential areas of the valve causing rapid reciprocation of the valve. The rapid reciprocation causes intermittent seating and unseating of a tip of the valve with a valve seat which permits the fuel to be injected into engine cylinders.
In one type of fuel injector, fuel at one pressure acts on one side of the valve to lift or unseat the valve for starting fuel injection, and fuel at another pressure acts opposite the one pressure to seat the valve for stopping fuel injection.
Another type of fuel injector utilizes fuel pressure acting on one side of the valve to lift or unseat the valve for starting fuel injection, and a high rate spring acts opposite the fuel pressure to seat the valve for stopping fuel injection.
The high rate springs are a costly item and are subject to breakage which of course requires replacement. Also, the forces created by such springs cause tip damage to the needle valves commonly used in such nozzles due to the high impact loads occurring when the valves seat.
Further, high impact loads caused by spring forces often create a resonance in the undamped spring which causes the needle valve to bounce. Such bounce permits undesirable leakage of fuel into an engine cylinder after injection. As a result, the leaked fuel is admitted to the cylinder out of cycle and thus is not fully consumed. This results in increased emissions and poor fuel economy.
The foregoing illustrates limitations of the known prior art. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations as set forth above.